In recent years, weight reduction of full vehicles arising from environmental problems has been advanced, in particular in the automotive industry, and analysis by computer aided engineering (hereinafter, referred to as “CAE (computer aided engineering) analysis”) has become an indispensable technique in designing automotive bodies. This CAE analysis has been known to achieve improvement in stiffness and weight reduction by using an optimization technique such as mathematical optimization, sheet thickness optimization, shape optimization, or topology optimization. For example, the optimization technique of the CAE analysis is often used in structural optimization of castings such as engine blocks. Of those optimization techniques of the CAE analysis, topology optimization, in particular, has started to attract attention.
Topology optimization is a method of providing a design space of a certain size, fitting three-dimensional elements in the design space, and leaving a minimum necessary portion of the three-dimensional elements satisfying given conditions, to thereby obtain an optimum shape satisfying the conditions. Therefore, for topology optimization, a method of directly constraining the three-dimensional elements forming the design space and directly adding a load thereon is used. As a technique related to such topology optimization, a method of topology optimization of a component of a complex structural body is disclosed in Japanese Patent Application Publication No. 2010-250818.
Structural bodies of automobiles and the like are configured by using mainly thin sheets, and when a portion of an automotive body formed of such a thin sheet is optimized, it is difficult to cause that portion to be independent as a design space and to reflect a load and a constrained state in that design space. Thus, there has been a problem that it is difficult to apply an optimization technique to a part of a structural body. Further, there has also been a problem of how to reflect an optimized shape in a thin sheet structure appropriately even if the optimized shape is found with three-dimensional elements.
The technique disclosed in Japanese Patent Application Publication No. 2010-250818 relates to a method of using mathematical operations and to a physical system for analysis, and does not provide any means of solving the above mentioned problems. In recent years, development of a technique to solve the above mentioned problems has been desired.
It could therefore be helpful to provide a technique that enables application of an optimization technique to a part of a structural body that receives external force and that contributes to optimization of the structural body.